This application relates to a testing apparatus, and more particularly to an apparatus for flame testing of materials such as building materials. It finds particular application in testing polyurethane roofing or insulation, but should not be limited to these particular building materials. Thus, the method and apparatus may find use with regard to related materials and testing.
It is common to expose building materials to combustion, and particularly test a sample under controlled procedures in order to determine the relative burning behavior as typically measured by the spread of the combustion flame, as well as measuring smoke that is developed during the test. For example, ASTM Standard E 84-06 entitled “Standard Test Method for Surface Burning Characteristics of Building Materials” discloses a fire test chamber that is a rectangular cross-section, horizontal tunnel or duct having multiple windows spaced longitudinally along the tunnel length. A building material sample is received in the test chamber or duct such that a first end is disposed adjacent a gas burner that delivers combustion flames against the surface of the test sample. A predetermined gas flow and regulated pressure delivers the combustion fuel and, in addition, induced airflow is provided to advance the flame along the sample. An exhaust fan is provided at the opposite end of the test apparatus to create the desired airflow.
In addition, a photometer or lamp photocell is mounted in the chamber to indicate the amount of smoke generated during the test. Similarly, one or more thermocouples are provided in the test chambers to record the temperature. The test apparatus is calibrated relative to red oak and/or fiber cement board test samples. Particularly, the flame spread distance, temperature, and change in the photoelectric cell readings as a result of testing these materials are used to assign values for a tested sample relative to these baseline values. For example, a flame spread index (FSI) is calculated on the progression of the flame over a longitudinal distance and in a certain amount of time.
In a similar manner, Underwriters' Laboratories, Inc. (UL) has its own standard test methods for fire tests for various building materials. For example, one such fire test for roof coverings is UL790 Standard. By way of example, the UL standard requires the test sample to be forty (40) inches wide by eight (8) feet long. The sample is prepared to a desired thickness. The sample must be cured for twenty-eight (28) days. A slope is provided in the test apparatus and the sample is mounted therein. The sample is then burned for ten (10) minutes with specified temperatures and wind speeds. By way of example only, a test limit for spread of flame is six (6) feet in length with no burn-off of the lateral edge. The test results are then tabulated and reported to the building materials manufacturer.
Substantially all building material manufacturers submit samples to either UL or Factory Mutual in order to determine the flammability (spread of flame) and how much smoke is generated by the material. A Steiner tunnel test requires a sample that is twenty-four (24) feet long, and two (2) feet wide to be submitted for these types of tests. As noted above, a flame is introduced at one end, a draft created at the other end, and the flame is observed as it moves toward the exhaust end over a ten (10) minute test, for example. A photometer determines the density of the smoke so that a smoke density ratio is also provided.
If the manufacturer finds the sample does not achieve the desired ratings as a result of conducting these tests, the manufacturer is relegated to creating new samples for submission and undertaking additional tests. This procedure can become cost prohibitive, For example, development of a new building material may result in a large number of tests as the manufacturer “tweaks” the formulation of the product. Each test costs approximately fifteen-hundred dollars ($1,500). Creating the sample and shipping the samples to the test laboratories may cost between three and five thousand dollars ($3,000-$5,000) per sample, and even then there is a three to four week delay in order to have the test completed. As will be appreciated, when hundreds of tests are undertaken, the cost, timing, etc. requires the manufacturer to limit the amount of research and development in creating new formulations, and/or be judicious with regard to the number of samples submitted for testing.
Thus, a need exists for a preliminary test that can be conducted on dimensionally scaled-down samples, at substantially reduced costs, and in a substantially reduced time frame.